The time-dependent stimulation of sodium halide salts on redox reactants, energy supply and luminescence in Vibrio fischeri

The excess of halide ions (F−, Cl−, Br−, I−) can cause adverse effects. Earlier studies demonstrated time-dependent stimulations of organic salts with halide ions on photobacteria. Therefore, inorganic ones with halide ions (e.g., NaX, X = F−, Cl−, Br−, I−) were assumed to cause similar effects. In the present study, Vibrio fischeri was exposed to NaX. Results showed that the contents of favin mono-nucleotide (FMN), nicotinamide adenine dinucleotide (NADH), and nicotinamide adenine dinucleotide phosphate (NADPH) were stimulated by NaX with a time-dependent fashion. The maximum stimulations on FMN at 24 h were 172%, 168%, 211% and 298% of the control (p < 0.05) in NaF, NaCl, NaBr and NaI, respectively, with an order of NaF ≈ NaCl < NaBr < NaI. The maximum stimulations on NAD(P)H at 24 h followed similar orders. Similar time-dependent stimulatory effects were observed in the FMN:NAD(P)H reaction catalyst (luciferase, in the form of expression levels of lux A and lux B), adenosine triphosphate and the expression levels of its regulating gene adk. The luminescent stimulations were significantly higher than the biochemical ones despite of similar time-dependence and stimulation order among NaX. The overall results showed a common hormetic pattern in sodium halide salts.